Both bus and tree topologies are characterized by the use of multipoint (1).For the bus, all stations attach, through appropriate hardware (2) known as a tap, directly to a linear transmission medium, or bus. Full-duplex operation between the station and the tap allows data to be transmitted onto the bus and received from the(3). A transmission from any station propagates the length of the medium in both directions and can be received by all other  (4). At each end of the bus is a (5) , which absorbs any signal, removing it from the bus.

空白（3）处应选择（）

A.tree

B.bus

C.star

D.ring

单点喷射系统是利用（）和（）来控制空燃比的。